From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anton Bondarenko Subject: Re: [PATCH v3 2/7] spi: imx: replace fixed timeout with calculated one Date: Tue, 10 Nov 2015 21:20:06 +0100 Message-ID: <56425176.9060805@gmail.com> References: <1446388901-6073-1-git-send-email-anton.bondarenko.sama@gmail.com> <1446388901-6073-3-git-send-email-anton.bondarenko.sama@gmail.com> <20151105084723.GI8526@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: broonie-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, b38343-KZfg59tc24xl57MIdRCFDg@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, vladimir_zapolskiy-nmGgyN9QBj3QT0dZR+AlfA@public.gmane.org, jiada_wang-nmGgyN9QBj3QT0dZR+AlfA@public.gmane.org To: Sascha Hauer Return-path: In-Reply-To: <20151105084723.GI8526-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> Sender: linux-spi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: On 05.11.2015 09:47, Sascha Hauer wrote: >> @@ -890,12 +891,40 @@ static void spi_imx_dma_tx_callback(void *cookie) >> complete(&spi_imx->dma_tx_completion); >> } >> >> +static int spi_imx_calculate_timeout(struct spi_imx_data *spi_imx, int size) >> +{ >> + unsigned long coef1 = 1; >> + unsigned long coef2 = MSEC_PER_SEC; >> + unsigned long timeout = 0; >> + >> + /* Swap coeficients to avoid div by 0 */ >> + if (spi_imx->spi_bus_clk < MSEC_PER_SEC) { >> + coef1 = MSEC_PER_SEC; >> + coef2 = 1; >> + } >> + >> + /* Time with actual data transfer */ >> + timeout += DIV_ROUND_UP(8 * size * coef1, >> + spi_imx->spi_bus_clk / coef2); >> + >> + /* Take CS change delay related to HW */ >> + timeout += DIV_ROUND_UP((size - 1) * 4 * coef1, >> + spi_imx->spi_bus_clk / coef2); >> + >> + /* Add extra second for scheduler related activities */ >> + timeout += MSEC_PER_SEC; >> + >> + /* Double calculated timeout */ >> + return msecs_to_jiffies(2 * timeout); >> +} > > I think you can simplify this function to: > > timeout = size * 8 / spi_imx->spi_bus_clk; > timeout += 2; > > return msecs_to_jiffies(timeout * MSEC_PER_SEC); > > The rationale is that when size * 8 / spi_imx->spi_bus_clk is 0 then we > can add another second and be fine. No need to calculate this more > accurate, in the end it's important to catch the timeout. If we do this > one or two seconds too late doesn't matter. > > Sascha > Sascha, What about something like this: timeout = size * (8 + 4) / spi_imx->spi_bus_clk; timeout += 2; return msecs_to_jiffies(2 * timeout * MSEC_PER_SEC); I think we still need to take into account 4 CLKs between each burst. Regards, Anton -- To unsubscribe from this list: send the line "unsubscribe linux-spi" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html